Upon arrival, homeowner stated that steam humidifier (model Aprilare 800) was making a knocking noise with usage. After thorough research and diagnosis, found that system is not meant to be operated with cold water due to solenoid valve opening and closing rapidly to cause water hammer. Removed shut off valve off of hot water line and installed to cold water line. Installed whole home Halo 5 water filtration system. Flushed 5 gallon gas water heater.